Enum ESSelectionStrategy 

pub enum ESSelectionStrategy {
    MuPlusLambda,
    MuCommaLambda,
}

Selection strategy for Evolution Strategies

Interaction with σ self-adaptation

Classical ES theory (Schwefel; Beyer & Schwefel 2002) shows that mutative step-size self-adaptation requires comma (MuCommaLambda) selection. Under plus/elitist selection an individual that happens to carry an over-small σ can survive indefinitely on the merit of its object variables, so badly-scaled strategy parameters are never purged and σ tends to collapse, stalling adaptation. The canonical self-adaptive recommendation is (μ,λ) with λ/μ ≈ 7 (e.g. (15, 100)). Consequently the default configuration (see ESConfig::default) pairs self-adaptation with comma selection; plus selection remains available as an explicit opt-in.

Variants

MuPlusLambda

(μ+λ): Select best μ from parents + offspring combined.

Elitist. Prefer this only when self-adaptation is disabled or when elitism is explicitly desired — see the type-level note on why elitism suppresses mutative σ self-adaptation.

MuCommaLambda

(μ,λ): Select best μ from offspring only (requires λ ≥ μ).

The correct pairing for mutative σ self-adaptation, and the default.

Trait Implementations

impl Clone for ESSelectionStrategy

fn clone(&self) -> ESSelectionStrategy

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ESSelectionStrategy

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ESSelectionStrategy

fn default() -> ESSelectionStrategy

Returns the “default value” for a type.